This specification relates to data storage for virtual machines.
Cloud computing is network-based computing in which typically large collections of servers housed in data centers or “server farms” provides computational resources and data storage as needed to remote end users. Some cloud computing services allow end users to run user-provided server software applications (e.g., e-commerce server applications, web servers, or file servers) in the cloud. Some other cloud computing services provide access to software applications such as word processors and other commonly used applications to end users who utilize the applications through web browsers or other client-side software. Users' electronic data files are usually stored in the server farm rather than on the users' personal computing devices.